Hello and thank you for reading my post.

I have two geographically distant places linked by a Cisco VPN.
In each place, there is a "bind" DNS server ("BS1" in place 1 and "BS2" in place 2).
Let's call "d1.com" the domain at place 1 and "d2.com" the domain at place 2.

So:
- The IPs at place 1 are in the range 192.168.10.0/24.
- The names at place 1 are "machine11.d1.com", "machine12.d1.com"...
- The IPs at place 2 are in the range 192.168.20.0/24.
- The names at place 2 are "machine21.d2.com", "machine22.d2.com"...

I would like to know how to configure each bind server "BS1" and "BS2" so that all the names can be solved through the VPN.
(The VPN is already working well with IPs).
For example, I would like to be able to do:
"ping machine21.d2.com" (and better: "ping machine21")
from "machine11.d1.com".

I have tried to add "forward" zone statements in "/etc/bind/named.conf.local" but either it's not the right way to proceed or I did it only wrongly or partly.

Can you please advise me how to do this?
Best regards.
Best wishes for 2014.